The present invention is directed to a process and apparatus for producing ultrafine explosive particles, and more particularly to an improved eductor device that produces ultrafine granular explosives which when incorporated into a binder system have the ability to propagate in thin sheets and have very low impact and very high propagation sensitivities.
Normally crystalline high explosives have been treated by various techniques to reduce their particle size. The particular particle size of explosives has a pronounced effect on its performance, and, generally the smaller the particles, the more sensitive the explosive is to reliable propagation sensitivity. Heretofore particles of high explosive have been prepared by dissolving the explosive in a solvent that is inert to the explosive and mixing the solvent with a liquid that is a nonsolvent for the explosive and is miscible with the solvent, or drowning the solution of explosive in the nonsolvent precipitating agent. Further, various modifications of these processes are known wherein, for example, additional nonsolvent is added to the turbulent mixture in order to produce fine crystals of high explosive, as described, for example, in British Patent No. 988,122, published Apr. 7, 1965. Such procedures have employed eductors or jet nozzles, as illustrated in Canadian Patent No. 533,487, for mixing one stream containing explosive dissolved in solvent and the other stream containing the nonsolvent precipitating agent. Such procedures produce small particles of high explosive, but the finely-divided explosives made by such methods do not consistently propagate detonations and are unreliable and erratic, especially when used in compositions wherein the particulate explosive is incorporated in a binder and the final product is formed into thin sheets or small diameter explosive cords. Therefore, a need exists for high explosives that can be used in such thin sheets or small diameter cords which consistently propagate detonation and exhibit a high order of propagation sensitivity and a low order of impact sensitivity.
The prior art discloses various processes and apparatus for making spheroidal ultrafine explosive particles. For example, see U.S. Pat. No. 2,329,575; 1,106,087; 2,715,574 and 3,754,061. More specifically, U.S. Pat. 3,754,061 discloses manufacturing crystalline high explosives into finely-divided spheroidal particles by mixing individual streams of a explosive solution with an inert nonsolvent solution by applying pressure against the flow of the nonsolvent stream, violently agitating the combined stream, and rapidly precipitating the explosive from the solution in the form of spheroidal particles permeated with microholes. The reference discloses injecting the two solutions at right angles to each other. However, this system has been found to be insufficient in that relatively large explosive particles preciptate in the area adjacent the nozzle in "dead spots". This necessarily reduces the area of explosive solution flow to a fraction of the theoretical value, and therefore adversly impacts the efficiency of the eductor since the explosive solution flow is channeled into only a portion of the nonsolvent stream thereby leading to relatively large particle size distribution. The large explosive particles which build up inside the eductor become dislodged when the eductor is under shut-down conditions and become blended with the desirable process stream during operating conditions. The result is that the final formulation contains a large quantity of relatively large explosive particles which add to the undesirable sensitivity of the explosive formulation to detonation by impact from, for example, a falling weight.